Group III-nitride based high electron mobility transistors (HEMTs) are attracting significant interest (e.g., for microwave and power switching applications). Electrically and thermally stable device schemes are essential for reaching the maximum potential of GaN devices. The reliability of Ni/Au-based Schottky gate metallizations has been limited by gate degradation from Ni migration into nearby metal and semiconductor layers when subjected to electrical and thermal stress. As such, development of alternative gate schemes resistant to these degradation mechanisms is highly desirable for fabrication of reliable HEMTs.
In conventional devices, nickel metal is in direct contact with III-nitride alloy material, such as gallium nitride. The nickel metal layer typically has a gold metal top layer. The nickel atoms are known to diffuse into the gallium nitride III-Nitride material with thermal stress, causing degraded Schottky to III-Nitride junction reliability, which is undesirable.
Features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.